Conventional heat protective layers are so called thermal barrier coatings (TBC) which are highly advanced material systems for formally insulating components from large and prolonged heat loads.
Current thermal barrier coatings (TBCs) may reach their application limits in high advanced gas turbines due to the limited capacities to control their micro-structure from the process parameters and the reduced choice of materials suitable for thermal plasma spraying. One way to overcome these limitations is to move away from the TBC coatings and replace them with so called ceramic tiles which can be fixed on the surface of the heat exposed component with different fastening technologies.
In the document U.S. Pat. No. 4,563,128 ceramic tiles are clamped in dovetail type recesses in the flank area of a turbine blade.
The document EP 0 895 028 B1 discloses a ceramic lining for combustions spaces comprising at least one wall panel, made of a heat resistant structural ceramic. Said wall panel provides an opening through which a fastening element, like a screw, being arranged for fastening said wall panel to the inner wall of the combustor.
Documents U.S. Pat. No. 7,198,860 B2 and US 2010/0260960 disclose ceramic tile insulation for gas turbine components with a multitude of ceramic tiles which are bonded to a heat exposed surface of a gas turbine component. A first layer of individual ceramic tiles are bonded to the surface of the gas turbine component which is of ceramic material. A second layer of individual tiles is bonded on top of the first layer. Multiple tiles may be attached to a flexible scrim, such as a woven ceramic cloth. These documents also describe that an entire sheet containing multiple tiles may be applied with adhesive to a gas turbine component.
A particular challenge is to cover at least those surface areas of a heat exposed component which suffer a special high temperature stress under working conditions with a multitude of single ceramic plate-like tiles which together shall form a uniform thermal protection layer surface. A particular challenge in this connection is to cover at least those surface areas of a heat exposed component which suffer a special high temperature stress during working conditions with a multitude of single ceramic plate like tiles which have to be handled and fixed onto the surfaces piece by piece. The curvatures and high thermal gradients imposed to those ceramic tiles require the use of smallest possible tiles to allow a good respect of the desired component shape and to limit risks of cracks occurring under high thermal gradients. Such ceramic tiles could be attached to the metal surface of the heat exposed components like turbine plates by brazing techniques. However the thermal expansion on the hot surface requires respecting a minimum tile distance to prevent them from mutually detaching themselves during expansion upon heating. It is a matter of fact that handling of each single ceramic tile to a defined position and bonding the tiles on the surface of the heat exposed component lead to a huge time and working expense which shall be reduced inventively.